Research On Performance Optimization Scheme Of PMSM Sensorless Control In Low Speed Section

Permanent magnet synchronous motors are widely used in various industries because of their small size,high reliability,high power density and high efficiency.However,the installation of the sensor increases the cost,takes up space,and is susceptible to various factors in some special environments,which reduces the reliability of the system.Sensorless control technology has significant advantages in these aspects,so it has become a research hotspot.In this thesis,the interior permanent magnet synchronous motor is taken as the investigation target.The sensorless control strategy of high frequency signal injection in low speed section is studied,and the corresponding optimization is made to improve the control accuracy and operation efficiency of the motor.Firstly,according to the difference of rotor structure,the mathematical models of surface-mounted and interior permanent magnet synchronous motors in different coordinate systems are established respectively.On this basis,several control strategies commonly used in vector control are introduced,and simulation is built to verify.Secondly,the sensorless control scheme in full speed range is introduced.The mathematical model of the motor under high frequency injection is established in the low speed section.The principle of the sensorless control scheme of rotating signal injection is studied.The heterodyne method is used instead of the arctangent to extract the rotor position.In order to simplify the decoupling process,the pulsating sinusoidal signal and the square wave signal are introduced into the sensorless control,and the rotor position error caused by the cross coupling effect is analyzed to improve the control accuracy of the system.The sensorless control scheme of sliding mode observer is briefly introduced in the middle and high speed section.Aiming at the chattering phenomenon of the system,the sigmoid function is used instead of the switching function to improve the observation accuracy.In the full speed domain control,the weighted method is used to achieve smooth switching from zero low speed to medium high speed.The above schemes are simulated and verified respectively to prove the effectiveness of the full speed range sensorless control algorithm.Then,for the dead time of the inverter in actual operation,the source of the sixth harmonic generated by the zero current clamping effect in the dead time is derived.The dead time is added to the traditional high frequency signal injection to observe the influence of zero current clamping effect on high frequency current.When the fundamental frequency current crosses the zero point,the induced high-frequency current repeatedly crosses the zero point at high frequency near the zero point,and the amplitude is not zero,so that the phase current also undergoes multiple zero-crossing phenomena,which deepens the zero-current clamping effect and causes distortion of high-frequency current.In view of this phenomenon,the reasons are analyzed through two different injection angles.On this basis,a pulse sine and square wave signal scheme based on special angle injection is proposed,which effectively suppresses the phenomenon of multiple zero crossings.A new rotor position error extraction scheme is proposed to analyze and experimentally compensate the cross-coupling effect under special angle injection.The sensorless control of the motor is realized while minimizing the zero current clamping effect.Verify on the simulation platform to prove the superiority of the scheme.Finally,the motor experimental platform is built to verify the above control scheme.The traditional and special high frequency signal injection algorithms are tested and compared under various working conditions to verify the effectiveness of sensorless control.The proposed high-frequency signal injection scheme based on special angle injection and cross-coupling compensation scheme are verified to improve the accuracy of sensorless control.